The present invention generally relates to self-calibrating time sources, and more specifically, to a self-calibrating time code generator that dynamically compensates for time delays to generate an accurate time code waveform.
A self-calibrating time source may be used to provide calendar and time-of-year information to a variety of devices for a variety of reasons. For example, sequential events recorders record occurrences of events, and then store a record of each occurrence in a report. The time of the occurrence of each event is also included with the event in the report. The time of the occurrence stored for each event is often derived from a time code generator. Thus, the more accurate the self-calibrating time source, the more accurate the recorded time of each event occurrence in the report.
Self-calibrating time sources may also be used to provide synchronization for various devices. For example, some devices are configured to take a number of measurements of an ongoing process at precisely predefined instants of time. Such a device may be required to measure a process parameter such as a voltage, a current, a temperature, a strain measurement, etc., once per second exactly on the second, (e.g., the measurements must be taken exactly at midnight, exactly one second after midnight, exactly two seconds after midnight, etc.). For example, digital fault recorders used in the power system industry require sampling of data from a power line, referenced to time. As a result, such devices often synchronize their measurement activities to a time code generator. Thus, the more accurate the self-calibrating time source, the more accurate the measurement timing.
Implementation of a time source often introduces inherent time delays. That is, the design of, and the components used to implement the time source are often responsible for inherent time delays during operation. Noise coupling into the time source, and loading or line-induced delays may also contribute to time delays. In addition, the time delays may dynamically vary over time, due to temperature variations or component aging. Such delays directly reduce the time accuracy and therefore the performance of the devices requiring the time information.